Gas temperature moderation within compressed gas vessel through heat exchanger

ABSTRACT

A pressure vessel for storing fuel cell reactants is disclosed. The pressure vessel includes an inner shell formed from a moldable material and forming a cavity therein, and an outer shell formed about the inner shell. A heat transfer member is disposed within the vessel cavity. The heat transfer member is thermally coupled a suitable external thermal mass external the pressure vessel to minimize the effect of thermal energy on the vessel. The heat transfer member may be a metallic structure within the cavity, or may be integrated within the inner shell on an inner shell surface. The external thermal mass may further be thermally coupled to either an active or a passive external thermal handling system for controlling the temperature of the fluid within the vessel.

FIELD OF THE INVENTION

The invention relates generally to a compressed gas container and, more particularly, to a compressed gas container for storing hydrogen gas on a vehicle for a fuel cell, wherein the container includes an inner heat exchange structure to militate against temperature fluctuations while the container is being filled with compressed gas, and while compressed gas is being extracted from the container.

BACKGROUND OF THE INVENTION

Hydrogen is a very attractive source of fuel because it is clean and can be used to efficiently produce electricity in a fuel cell. The automotive industry expends significant resources in the development of hydrogen fuel cells as a source of power for vehicles. Such vehicles would be more efficient and generate fewer emissions than vehicles employing internal combustion engines.

A hydrogen fuel cell is an electro-chemical device that includes an anode and a cathode with an electrolyte therebetween. The anode receives hydrogen gas and the cathode receives oxygen. The hydrogen gas is ionized in the anode to generate free hydrogen ions and electrons. The hydrogen ions pass through the electrolyte to the cathode, and react with the oxygen and electrons in the cathode to generate water as a bi-product. The electrons from the anode cannot pass through the electrolyte, and are directed through a load to perform work before being sent to the cathode. The work acts to operate the vehicle or systems on the vehicle. Many fuel cells are combined in a stack to generate sufficient power to drive a motor vehicle.

A fuel cell can include a processor that converts a liquid fuel such as alcohols (methanol or ethanol), hydrocarbons (gasoline), and/or mixtures thereof such as blends of ethanol/methanol and gasoline, to hydrogen gas for the fuel cell. Such liquid fuels are easy to store on the vehicle. Further, there is a nationwide infrastructure for supplying liquid fuels. Gaseous hydrocarbons, such as methane, propane, natural gas, LPG and, etc., are also suitable fuels for both vehicle and non-vehicle fuel cell applications. Various processors are known in the art for converting the liquid fuel to gaseous hydrogen suitable for the fuel cell.

Alternatively, hydrogen gas can be processed separate from the vehicle and stored at filling stations and the like. The hydrogen gas is transferred from the filling station to pressurized tanks or containers on the vehicle to supply the desired hydrogen gas to the fuel cell as needed. Typical pressures within compressed hydrogen gas containers for fuel cell applications are in the range of 200 bar-700 bar (2900-10,150 psi).

Because of the high pressures involved, it is desirable for storage containers for compressed gases to have mechanical stability and integrity. It is also desirable to make hydrogen gas containers on vehicles lightweight so as not to significantly affect the weight requirements of the vehicle, or to improve performance, or both. The current trend in the industry is to employ type 4 compressed gas tanks for storing compressed hydrogen gas on the vehicle. A type 4 tank includes an outer structural layer made of synthetic material, such as a glass fiber or a carbon fiber wrap, and an inner plastic liner. The outer layer provides the structural integrity of the tank for the pressure contained therein, while the plastic liner provides a gas impermeable vessel for sealing the gas therein. Typically, the plastic liner is first formed by a molding process, after which the fiber wrap is formed around the liner and adhered thereto.

FIG. 1 shows a compressed gas vessel 10 currently contemplated in the industry to store compressed hydrogen gas on a vehicle for fuel cells. The vessel 10 is cylindrical in shape to provide the desired structural integrity, and includes an outer structural wall 12 and an inner liner 14 defining a container chamber 16 therein. The outer wall 12 is typically made of a suitable fibrous interconnected synthetic wrap such as filament wound glass or carbon fiber wrap, and has a sufficient thickness to provide the desired mechanical rigidity for pressure containment. The liner 14 is typically made of a suitable high-density polymeric material such as polyethylene, PET, ethylene vinyl alcohol, or an ethylene vinyl acetate terpolymer, to provide a substantially hydrogen impermeable containment vessel within the vessel 10. The thickness of the liner 14 is generally about 5 mm. Thus, the combination of the outer wall 12 and the liner 14 provides the desired structural integrity, pressure containment and gas tightness in a light-weight and cost effective manner.

The vessel 10 includes an adapter or boss 18 that provides the inlet and outlet openings for the hydrogen gas contained therein. The adapter 18 is typically a steel structure that houses the various valves, pressure regulators, piping connectors, excess flow limiters, and the like, that allow the vessel 10 to be filled with the compressed hydrogen gas, and allow the compressed gas to be discharged from the vessel 10 at or near ambient pressure, or at a desired pressure, to be sent to the fuel cell. The adapter 18 is typically made of steel to provide the structure desired for storing compressed hydrogen gas. The adapter 18 may be formed of any metal or metal alloy compatible with hydrogen that is suitable for the pressure levels within the vessel 10. A suitable adhesive, sealing ring, or the like (not shown) is employed to seal the liner 14 to the adapter 18 in a gas tight manner, and secure the adapter 18 to the outer wall 12.

During a vessel filling process, a fill gas 20 flows into the vessel 10 from one end 22 of the vessel 10 to an opposite end 24 of the vessel 10 and becomes contained gas 26. As the filling process proceeds, the pressure in the vessel 10 increases. It is desirable that the temperature of the fill gas 20 is near ambient temperature (300 K., 27° C.) and be at a suitable pressure to fill the vessel 10 within a few minutes (less than three minutes). However, as a result of the thermodynamic properties of the fill gas 20 and the contained gas 26, compression causes the contained gas 26 to be heated in response to the fill gas 20 being introduced therein under pressure. As a result, the temperature of the contained gas 26 within the vessel 10 rises, because there is no significant heat transfer from the gas into the vessel and further into the environment during the fill process. The relationship between increased pressure and increased temperature during a filling (i.e. refueling) process is illustrated in FIG. 2 to the left of dashed line 30.

The heating of the contained gas 26 within the vessel 10 causes an undesirable temperature rise within the plastic liner 14, which may affect the gas sealing ability of the liner 14. Therefore, it is necessary to control the temperature of the contained gas 26 within the vessel 10 while the vessel 10 is being filled and thereafter. In fact, for composite vessels with plastic liners, the gas temperature within the vessel is a limiting factor for the refueling time. It is not uncommon that the refueling has to be slowed down or interrupted because of the gas temperature in the vessel. This can even be the case if the fill gas 20 is pre-cooled at the filling station.

Removal of gas from the vessel 10 results in the opposite problem, as illustrated in FIG. 2 to the right of the dashed line 30. For example, during operation of the fuel cell as gas is withdrawn from the pressure vessel, the temperature within the vessel drops significantly. If left alone, the temperature could fall below a minimum desired operation temperature of the vessel material or neighboring components. Known techniques to prevent too low of a temperature within the vessel include heaters applied to the vessel 10 or to the adapter 18, or flow reductions of the extracted gas. Heaters consume energy produced by the fuel cell that otherwise would be used to operate the vehicle. Flow reductions of the extracted gas operate to limit the power output by the fuel cell, thereby affecting operation of the vehicle.

It would be desirable to develop a hollow pressure vessel adapted to minimize the effect of thermal energy on the vessel, by providing a heat transfer between the fill gas and the outside environment while also minimizing the assembly and material costs thereof.

SUMMARY OF THE INVENTION

Concordant and congruous with the present invention, a hollow pressure vessel adapted to minimize the effect of thermal energy on the vessel, while also minimizing the assembly and material costs thereof, has surprisingly been discovered.

In one embodiment, a vessel comprises an inner shell formed from a moldable material and forming a cavity therein; an outer shell formed over the inner shell; and a heat transfer member integrated within the vessel, the heat transfer member thermally coupled to the environment to minimize the effect of thermal energy on the vessel. The heat transfer member may be a metallic sheet structure within the cavity, or may be integrated within the inner shell on an inner shell surface. The heat transfer member may be thermally coupled to a suitable external thermal mass for controlling the temperature of a fill gas.

In another embodiment, a vessel comprises an inner shell formed from a moldable material and forming a cavity therein; an outer shell formed over the inner shell; and a heat transfer member integrated within the vessel, the heat transfer member thermally coupled to the environment to minimize the effect of thermal energy on the vessel. The heat transfer member may be a metallic sheet structure within the cavity, or may be integrated within the inner shell on an inner shell surface. The heat transfer structure is thermally coupled to an active external thermal system for controlling the temperature of fill gas.

DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which:

FIG. 1 is a schematic cross-sectional elevational view of a pressure vessel as known in the art;

FIG. 2 is a graphical representation of the relationship of pressure and temperature of a fill gas to time during a typical refueling/filling process and a typical extraction/driving process;

FIG. 3 is schematic cross-sectional elevational view of a vessel according to an embodiment of the invention; and

FIG. 4 is a schematic cross-sectional elevational view of a vessel according to another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed, the steps presented are exemplary and nature, and thus, the order of the steps is not necessary or critical.

FIG. 3 illustrates a hollow pressure vessel 110 having an outer structural wall 112 and an inner liner 114 defining a vessel chamber 116 therein. Like the vessel 10 of FIG. 1, the vessel 110 has a substantially cylindrical shape and is adapted to hold a pressurized fluid 126. It is understood that the vessel 110 may have any shape as desired, and the vessel 110 may include additional layers such as a barrier layer, a foil layer, a porous permeation layer, and the like, as desired, similar to those disclosed in commonly-owned U.S. patent application Ser. No. 11/847,007 and U.S. patent application Ser. No. 11/956,863, both hereby incorporated herein by reference in their entireties. The pressurized fluid 126 may be any fluid such as hydrogen gas and oxygen gas, a liquid, and both a liquid and gas, for example.

The inner liner 114 of the vessel 110 is a hollow container adapted to store the pressurized fluid 126. As shown, the inner liner 114 is formed from a layer of polymer material, but the inner liner 114 may be formed from multiple layers, as desired. The inner liner 114 may be formed by blow molding, extrusion blow molding, rotational molding, or any other suitable process. In the embodiment shown, the inner liner 114 has a substantially cylindrical shape. However, the inner liner 114 may have any shape, as desired. The inner liner 114 may be formed from a plastic such as polyethylene, PET, ethylene vinyl alcohol, or an ethylene vinyl acetate terpolymer. The inner liner 114 may also be formed from other moldable materials such as a metal, a glass, and the like, chosen to minimize escape or diffusion of the pressurized fluid 126.

The outer structural wall 112 of the vessel 110 is disposed on the inner liner 114. The outer structural wall 112 has a substantially cylindrical shape, and substantially abuts the inner liner 114 to provide structural support for the vessel 110, allowing the vessel 110 to withstand high pressures. The outer structural wall 112 may be formed from any moldable material such as a metal and plastic, for example, or the outer structural wall 112 may be formed with a filament winding process or other process. If the outer structural wall 112 is formed by a filament winding process, the outer structural wall 112 may be formed from a carbon fiber, glass fiber, a composite fiber, a fiber having a resin coating, and the like, for example. It is understood that the material used to form the outer structural wall 112 may be selected based on the process used to affix the outer structural wall 112 to the inner liner 114, the use of the vessel 110, and the properties of the fluid to be stored in the vessel 110.

Like the vessel 10 of FIG. 1, the vessel 110 includes an adapter 118 attached at a vessel first end 122 that provides the inlet and outlet opening for the pressurized fluid 126 contained therein. As noted previously, the adapter 118 is typically a steel structure that houses the various valves, pressure regulators, piping connectors, access flow limiter's, etc., that allow the vessel 110 to be filled with the fill gas 120 that becomes the pressurized fluid 126, and allow the pressurized fluid 126 to be discharged from the vessel 110 at or near ambient pressure, or any desired pressure, to be sent to the fuel cell. A suitable adhesive, sealing ring, or the like (not shown) is employed to seal the inner liner 114 to the adapter 118 in a gas tight manner as is known in the art. Similarly, conventional means are used to secure the adapter 118 to the outer structural wall 112 of the hollow vessel 110.

A heat transfer member 130 is located within the hollow vessel 110, and more specifically, within the inner liner 114 and within the vessel chamber 116. The heat transfer member 130 shown in FIG. 3 is shown as a metallic structure within the vessel cavity or chamber 116. The heat transfer member 130 may include a center support 132 and a plurality of fins or arms 134 integrally connected or thermally connected to the center support 132. The center support 132 is thermally connected to the adapter 118 at a center support first end 136. In one embodiment, a center support second end 138 is thermally connected to a second adapter or boss 140 embedded within a vessel second end 124. The fins 134 project outwardly from the center support 132 within the vessel chamber 116. The fins 134 are sized and designed to extend sufficiently within the vessel cavity 116 to provide a desired thermal interaction with the pressurized fluid 126. The fins 134 may also contact the inner surface 128 of the inner liner 114. In one embodiment, at least a portion 158 of the fins 134 are formed on the inner surface 128 of the inner line 114.

Both the adapter 118 and the boss 140 may act as heat sinks due to the thermal mass of each of the adapter 118 and the boss 140. Additionally, one or both of the adapter 118 and the boss 140 may be thermally coupled to heat exchange structures 142, 144, respectively. The heat exchange structures 142, 144 may comprise additional thermal masses 146, 148, respectively, such as valve blocks used to control the extraction of gases from the vessel 110, or the like. The thermal masses 146, 148 may be actively or passively cooled, and any heat removed by the thermal masses 146, 148 may be stored or may be utilized to control the temperature of other areas of the gas extraction system, thereby enhancing the efficiency of the design. As a non-limiting example, heat extracted and stored within the thermal masses 146, 148 during a refueling event, when the temperature of the pressurized fluid 126 rises, may be used to heat the gas 120 as it is extracted from the vessel 110 during operation of the fuel cell, or may be used to elevate the temperature of the pressurized fluid itself during extraction of the gas 120 from the vessel 110.

During refueling operations (i.e. within the regime shown to the left of dashed line 30 in FIG. 2), as the fluid 120 is added to the hollow vessel 110, both the pressure 32 and the temperature 34 of the pressurized fluid 126 within the vessel rise. The heat produced during the fill process flows through the heat transfer member 130, and is conducted from the fins 134 to the center support 132, and from there into both the adapter 118 and the boss 140. As a result, heat is extracted from the pressurized fluid 126 and conducted out of the vessel 110, thereby controlling the temperature within the vessel 110. If the thermal mass of the adapter 118 and the boss 140 is sufficiently large, the temperature within the vessel 110 may be maintained below the desired point without a further heat sink. Alternatively, a suitable heat dissipating structure such as the thermal masses 146, 148 could store the heat or transfer the heat to the environment, such as through external fins 160, or through a radiator (not shown), or the like.

During periods of fluid extraction from the vessel 110 (i.e. within the regime shown to the right of the dashed line 30 in FIG. 2), as the fluid 120 is extracted from the hollow vessel 110, the pressure 32′ and the temperature 34′ of the pressurized contained fluid 126 within the vessel drop. In this operating regime, external heat is conducted from the thermal masses 146, 148 through the adapter 118 and the boss 140, respectively, and is further conducted into the respective first and second ends 136, 138 of the center support 132, where it may be further conducted into the fins 134 to support heating of the pressurized fluid 126 within the vessel 110. Heat from outside of the vessel 110 is therefore made available to the vessel chamber 116 to maintain the operating temperature of the pressurized fluid 126 above any minimum desired operating temperature of the vessel 110. As noted previously, the thermal masses 146, 148 may be passively or actively heated and cooled. Passive thermal masses 146, 148 may take the form of a large metallic mass, and may include fins 160 or other desired passive heat radiating structure.

With reference to FIG. 4, a further embodiment of the invention including an active thermal handling system is described. For the purpose of clarity, like structures from FIG. 3 have the same reference numerals and are denoted with a prime (640) symbol.

In the embodiment shown in FIG. 4, the adapter 118′ and the boss 140′ may include passages 150, 152, respectively, to allow a heat exchange fluid 154 to flow through the adapter 118′ and the boss 140. The passages 150, 152, and hence the adapter 118′ and the boss 140′, are thermally coupled to thermal masses 146′, 148′ to allow heat from the vessel chamber 116′ to be stored or transferred to the environment. Favorable results have been obtained when the passages 150, 152 are coupled to the climate control system of a motor vehicle powered by the fuel cell. Thus, the heat transfer member 130′ may be heated or cooled by the heating and air-conditioning system of the motor vehicle. Alternatively, the heat exchange fluid 154 may be a fluid that undergoes a phase change as it is either heated or cooled. Such a phase changing fluid may further conduct heat from the adapter 118′ and the boss 140′ to thermal masses 146′, 148′, and from there to an exterior heat exchange structure 142′, 144′, such as fins 160′, a radiator (not shown) or the like. In this way, the heat transfer member 130′ within the vessel 110′ may be thermally coupled to any exterior heat exchanger, as desired.

While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the disclosure, which is further described in the following appended claims. 

1. A vessel comprising: an inner shell forming a cavity therein; an outer shell formed over the inner shell; and a heat transfer member disposed within the cavity to provide thermal communication between the cavity and outside of the cavity, the heat transfer member adapted to minimize an effect of thermal energy on the vessel.
 2. The vessel of claim 1, wherein the heat transfer member is thermally coupled to a heat exchange structure external the outer shell for controlling a temperature in the cavity.
 3. The vessel of claim 1, wherein the heat transfer member is a metallic sheet structure disposed within the cavity.
 4. The vessel of claim 3, wherein the heat transfer member further comprises: a center support; and at least one fin thermally coupled to and extending substantially outwardly from the center support.
 5. The vessel of claim 4, wherein the at least one fin contacts at least a portion of an inner surface of the inner shell.
 6. The vessel of claim 5, further comprising: a first adapter having a first thermal mass at a vessel first end, the first adapter sealingly engaging at least one of the inner shell and the outer shell and extending therethrough; and a second adapter having a second thermal mass at a vessel second end, the second adapter sealingly engaging at least one of the inner shell and the outer shell and extending therethrough; wherein the center support is thermally coupled to the first adapter and the second adapter.
 7. The vessel of claim 6, wherein at least one of the first and second thermal masses is thermally coupled to an external heat exchange structure for controlling the temperature in the cavity.
 8. The vessel of claim 1, further comprising: a first adapter having a first thermal mass disposed at a vessel first end, the first adapter sealingly engaging at least one of the inner shell and the outer shell and extending therethrough; and a second adapter having a second thermal mass disposed at a vessel second end, the second adapter sealingly engaging at least one of the inner shell and the outer shell and extending therethrough; wherein the center support is thermally coupled to the first adapter and the second adapter.
 9. The vessel of claim 8, wherein at least one of the first adapter and the second adapter is thermally coupled to a heat exchange structure.
 10. The vessel of claim 9, wherein the heat exchange structure is one of a radiator and a heating and air conditioning system.
 11. The vessel of claim 8, wherein one of the first adapter and the second adapter further includes an internal passage formed therein for receiving a heat exchange fluid, the fluid in thermal communication with a heat exchange structure.
 12. The vessel of claim 11, wherein the heat exchange structure is an active cooling system.
 13. The vessel of claim 11, wherein the heat exchange structure is one of a radiator and a heating and air conditioning system,
 14. A vessel comprising: an inner shell formed from a moldable material and forming a cavity therein; an outer shell formed over the inner shell; and a metallic structure disposed within the cavity adapted to minimize an effect of thermal energy on the vessel, wherein the metallic structure is thermally coupled to a heat exchange structure external the outer shell for controlling a temperature in the cavity.
 15. The vessel of claim 15, wherein the metallic structure is in thermal communication with at least a portion of an inner surface of the cavity.
 16. The vessel of claim 16, further comprising: an adapter sealingly engaging at least one of the inner shell and the outer shell and extending therethrough; wherein the metallic structure is thermally coupled to the adapter.
 17. The vessel of claim 17, wherein the adapter is further thermally coupled to an external heat exchanger.
 18. A vessel, comprising: a hollow inner shell formed from a moldable material and forming a cavity therein; an outer shell formed over the inner shell; an adapter sealingly engaging at least one of the inner shell and the outer shell and extending therethrough; a heat transfer member disposed within the cavity and thermally coupled to the adapter to minimize an effect of thermal energy on the vessel.
 19. The pressure vessel of claim 19, wherein the heat transfer member is a metallic structure, comprising: a center support; and at least one fin thermally coupled to and extending substantially outwardly from the center support. 